The present invention relates to cable trays for use with electrical cables.
Cable trays are used to support electrical cables which run through factories and other structures. Cable trays may have straight and (horizontally and vertically) curved sections to accommodate the installation requirements of a particular setting.
One type of known cable tray has a pair of parallel side rails or stringers that are interconnected with a plurality of transverse rungs at predetermined intervals along the length of the parallel side rails. Cables are laid on top of the rungs. The rungs are typically attached to the side rails by fasteners, or are welded to the side rails. The parallel side rails may be joined end-to-end by a splice plate or a connecting bar. However, since these cable trays generally do not secure the cables in spaced relation to each other, they may be unsuitable for use with high power cables where there may be a need to keep the cables cool, or to prevent the cables flailing in the event of a fault or short circuit.
A cable tray more suited to high power cables is disclosed in U.S. Pat. No. 3,618,882 to Podedworny. In Podedworny, two abutting support blocks with semi-circular cut-outs on adjacent faces provide a housing with cylindrical openings that confine the cables in spaced relation in the cable tray. The blocks are secured to each other and to a rung by bolts extending vertically through the blocks and into the rung.
To install the type of cable tray disclosed by Podedworny, lower support blocks may be placed on rungs with their semi-circular face facing upwardly and the lower support blocks may be temporarily held in place by bolts. Cables may then be laid into the semi-circular channels without risk of the support blocks shifting or falling over. Next, the bolts may be removed, the upper support blocks set in place and the bolts again inserted to complete the assembly. This manner of assembly is time consuming and may become difficult where the tray has a large vertical curve. More specifically, with a large vertical curve, as it becomes hard to keep a lower support block properly positioned while the bolts are inserted and there is also a risk of the lower support block shifting when the bolts are removed preparatory to installing the upper support blocks.